High-load linear actuator

ABSTRACT

A high-load linear actuator includes a driving mechanism, a worm shaft, a worm wheel assembly, a lead screw, a telescopic pipe and an outer pipe. The driving mechanism includes a base and a motor. The base has a supporting portion and an accommodating portion. The motor is fixed to the supporting portion. The worm shaft extends from the motor into the supporting portion. The worm wheel assembly includes a worm wheel and two bearings for supporting the worm wheel in the accommodating portion. The worm wheel is engaged with the worm shaft. The lead screw is disposed through the worm wheel and driven by the motor for rotation. The telescopic pipe slips on the lead screw to be threadedly connected therewith. The outer pipe slips on the telescopic pipe. The rotation of the lead screw drives the telescopic pipe to linearly extend or retract relative to the outer pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 13/045,650 filed on Mar. 11, 2011. The entire disclosure isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an actuator, in particular to ahigh-load linear actuator used for equipments such as a medicalapparatus and an electric chair.

BACKGROUND OF THE INVENTION

As the economic development of our society advances and people eathigh-nutrition high-calorie foods more often, our average body weightincreases constantly, so that medical apparatus or electric chairrelated manufacturers keep designing and introducing improved linearactuators for the aforementioned equipments to meet market requirements.

The conventional linear actuator mainly uses driving components such asa motor together with a worm shaft and a worm wheel to drive and rotatea lead screw, while driving a telescopic pipe screwed with the leadscrew and extending or retracting the telescopic pipe linearly. Theforegoing components are combined to constitute a linear actuator.

Since the conventional linear actuator can be used for a low-loadmedical apparatus, it cannot satisfy incremental product requirements ofa high-load linear actuator if safe load and lifespan are taken intoconsideration. Furthermore, a linear actuator applied to a high-loadequipment has a telescopic pipe moving at a speed which will affect thecomfort and safety of users. Therefore, the conventional linear actuatorrequires improvements.

In view of the aforementioned shortcomings of the prior art, theinventor of the present invention based on years of experience in therelated industry to conduct extensive researches and experiments, andfinally developed a feasible solution in accordance with the presentinvention to overcome the shortcomings of the prior art.

SUMMARY OF THE INVENTION

Therefore, it is a primary objective of the present invention to providea high-load linear actuator that uses the structure of a drivingmechanism and a worm wheel assembly to provide a stable support, suchthat the linear actuator can be applied to high-load equipments.

To achieve the foregoing objective, the present invention provides ahigh-load linear actuator, comprising a driving mechanism, a worm shaft,a worm wheel assembly, a lead screw, a telescopic pipe and an outerpipe. The driving mechanism has a base and a motor that can be rotatedclockwise and counterclockwise, and the base has a supporting portionand an accommodating portion, and the supporting portion has a seat anda hollow cylinder formed and extended from the seat, and theaccommodating portion has a ring body coupled to the hollow cylinder,and the motor is mounted onto the seat. The worm shaft is protruded fromthe motor and passed into the hollow cylinder. The worm wheel assemblyhas a worm wheel and two bearings for jointly supporting the worm wheelinstalled inside the ring body, and the worm wheel is engaged andtransmitted with the worm shaft. The lead screw is passed through andcoupled to the worm wheel, and actuated by the motor to produce arotation. The telescopic pipe is sheathed onto the exterior of the leadscrew and screwed with the lead screw; and the outer pipe is sheathedonto the exterior of the telescopic pipe, and the telescopic pipe isrotated and driven by the lead screw to extend or retract linearly withrespect to the outer pipe.

The present invention also has the following effects and uses a designof the base and the worm wheel assembly to achieve the effects ofenhancing the stability of supporting the worm wheel in the ring bodyand reducing the assembling and disassembling time for installation,repair and maintenance. With the installation of the retardationtransmission mechanism and the friction of each rolling needle with theintermediate ring, the lead screw can be rotated in a specific directionand hindered to achieve the retardation effect. The intermediate ring isused for rotating the torque spring easily, such that the transmissionmechanism has a good transmission performance. When the lead screw ispushed by a force in an opposite direction, the intermediate ring, eachrolling needle, the driven bushing and the lead screw will not produce arelative transmission, so that the lead screw can be fixed securely toprevent the lead screw from sliding out from the nut effectively. Thefriction produced between the transmission components increases with theload, so that if there is no load, there will be no unnecessary frictionor any power consumption. The telescopic pipe retracted at a speedsubstantially the same for different loads, and thus the telescopic pipecan be descended at a constant speed, and the actuator can be usedcomfortably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a linear actuator of the presentinvention;

FIG. 2 is an exploded view of a driving mechanism and a worm wheelassembly of the present invention;

FIG. 3 shows FIG. 2 from another viewing angle;

FIG. 4 is a cross-sectional view of each component of FIG. 2:

FIG. 5 is an exploded view of a linear actuator of the presentinvention;

FIG. 6 is an exploded view of a retardation transmission mechanism ofthe present invention;

FIG. 7 is a cross-sectional view of a retardation transmission mechanismof the present invention;

FIG. 8 is a perspective view of a linear actuator of the presentinvention; and

FIG. 9 is a cross-sectional view of a linear actuator of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The technical characteristics and contents of the present invention willbecome apparent with the following detailed description and relateddrawings. The drawings are provided for the purpose of illustrating thepresent invention only, but not intended for limiting the scope of theinvention.

With reference to FIG. 1 for a high-load linear actuator of the presentinvention, the actuator is primarily applied to a load of hundreds orthousands of kilograms, and the high-load linear actuator comprises adriving mechanism 10, a worm shaft 20, a worm wheel assembly 30, a leadscrew 40, a telescopic pipe 50 (as shown in FIG. 8) and an outer pipe60.

With reference to FIGS. 2 to 4, the driving mechanism 10 includes a base11 and a motor 12 which can be rotated clockwise and counterclockwise.The base 11 has a supporting portion 111 and an accommodating portion115, and the supporting portion 111 is formed by a plate-shaped seat 112and a hollow cylinder 113 extended upwardly from the seat 112. The motor12 is mounted to the bottom of the seat 112 by screws (not shown in thefigures). The accommodating portion 115 has a circular ring body 116 anda cover plate 117, and the circular ring body 116, the seat 112 and thehollow cylinder 113 are integrally formed. In addition, a rear step 1161is formed on an internal side of the circular ring body 116, and thecover plate 117 is secured to a lateral edge of the circular ring body116 by screws (not shown in the figures), and a front step 1171 isformed on a side of the cover plate 117 and corresponsive to thecircular ring body 116 (as shown in FIG. 3).

The worm shaft 20 can be an axle of the motor 12 and protrudes from thecenter of the motor 12, or connected to and extended from the center ofmotor 12. When the motor 12 is fixed to the seat 112, the worm shaft 20is passed into the hollow cylinder 113, and a free end of the worm shaft20 is installed to the hollow cylinder 113 by a bushing to enhance thefixing stability.

The worm wheel assembly 30 comprises a worm wheel 31, a front bearing 32and a rear bearing 33, and the worm wheel 31 has a circular tooth flank311, a hollow axle 312 coupled to the circular tooth flank 311, andfront and rear containing grooves 313, 314 formed between the circulartooth flank 311 and the hollow axle 312. In addition, a plurality ofinternal gear teeth 315 are installed at a rear side of the hollow axle312 (as shown in FIG. 3), and the circular tooth flank 311 is engagedand transmitted with the worm shaft 20. With reference to FIG. 4, thefront bearing 32 is sheathed on the hollow axle 312 and contained in thefront containing groove 313, a portion of an area of the externalperiphery of the front bearing 32 is exposed from the circular toothflank 311, and the exposed area of the front bearing 32 is fixed intothe front step 1171 of the cover plate 117. Similarly, the rear bearing33 is sheathed on the hollow axle 312 and contained in the rearcontaining groove 314, and a portion of an area of the externalperiphery of the rear bearing 33 is exposed from the circular toothflank 311, and the exposed area of the rear bearing 33 is fixed into therear step 1161 of the circular ring body 116, such that the worm wheel31 can be supported jointly by the circular ring body 116 and the coverplate 117 in the accommodating portion 115.

With reference to FIG. 5, the lead screw 40 has a threaded section 41and a circular shaft section 42 extended from the threaded section 41.An external positioning plane 421 is formed at an end of the circularshaft section 42 and away from the threaded section 41, and an end ofthe lead screw 40 is passed into the hollow axle 312 of the worm wheel31 (as shown in FIG. 9), and the other end of the lead screw 40 isextended outwardly in a direction away from the base 11, and the leadscrew 40 is driven by the motor 12 to drive the worm shaft 20 and theworm wheel 31 to produce a rotation.

The telescopic pipe 50 has a pipe body 51, a nut 52 fixed to a distalportion of the pipe body 51 and screwed and transmitted with the leadscrew 40 (as shown in FIG. 9), and a plurality of embedding lumps 521protruded from the external periphery of the nut 52.

The outer pipe 60 is sheathed onto the exterior of the pipe body 51 ofthe telescopic pipe 50 (as shown in FIG. 1), and the outer pipe 60includes a plurality of trenches 61 (as shown in FIG. 9) formed thereinand provided for embedding each embedding lump 521 to limit the rotationof the telescopic pipe 50. After the telescopic pipe 50 is driven by therotation of the lead screw 40, the telescopic pipe 50 extends orretracts linearly with respect to the outer pipe 60.

The linear actuator of the present invention further comprises a rearsupporting mechanism 65 (as shown in FIG. 5) including two half covers651 and a roller bearing 652 clamped and fixed jointly by the two halfcovers 651, and the roller bearing 652 is provided for passing, couplingand installing an end of the lead screw 40 to enhance the stability ofoperating the lead screw 40 and the telescopic pipe 50. In addition, anotch 653 is formed at the joint of the two half covers 651.

With reference to FIGS. 6 and 7, the linear actuator of the presentinvention further comprises a retardation transmission mechanism 70sheathed and coupled to the lead screw 40 and disposed between the rearsupporting mechanism 65 and the worm wheel assembly 30. The retardationtransmission mechanism 70 comprises a driven gear 71, a gripper ring 72,a driven bushing 73, a plurality of rolling needles 74, an intermediatering 75, a torque spring 76 and a position-limiting catch cover 77. Thedriven gear 71 is sheathed and coupled to a position of the circularshaft section 42 of the lead screw 40 and has a portion passed andcoupled to a plurality of external gear teeth 711 of the internal gear315 of the worm wheel 31. The gripper ring 72 has a plurality ofratcheted grooves 721 latched with the external gear teeth 711respectively, a plurality of gripper arms 722, and a separating slot 723formed between any two adjacent gripper arms 722.

The driven bushing 73 has an internal positioning plane 731, a pluralityof protruding stripes 732 extended from the external periphery of thedriven bushing 73, and a ditch 733 formed between any two adjacentprotruding stripes 732. The driven bushing 73 is sheathed and coupled tothe lead screw 40, and the internal positioning plane 731 and theexternal positioning plane 421 of the circular shaft section 42 areembedded with each other and rotated together, and the driven bushing 73is contained in each gripper arm 722 of the gripper ring 72. Eachrolling needle 74 is inserted and coupled into a space enclosed by eachseparating slot 723 and each ditch 733. The intermediate ring 75 issheathed and coupled to the external periphery of the gripper ring 72and contacted with each rolling needle 74. The torque spring 76 includesa positioning section 761 bent from the torque spring 76, and the torquespring 76 is bound with the external periphery of the intermediate ring75 by an elastic force, and the positioning section 761 is passed andfixed into the notch 653. The position-limiting catch cover 77 issheathed and coupled to a side of the driven bushing 73 to seal distalsurfaces of the gripper ring 72 and each rolling needle 74 (as shown inFIG. 9).

With reference to FIGS. 8 and 9, the linear actuator of the presentinvention further comprises a housing 80 covered onto the exterior ofthe driving mechanism 10 and the retardation transmission mechanism 70and supported by the rear supporting mechanism 65 for passing a side ofthe outer pipe 60.

In addition, the linear actuator of the present invention furthercomprises an electric unit 90 (as shown in FIG. 1) installed in thehousing 80 and disposed on a lateral edge of the motor 12.

In FIG. 8, when the worm wheel 31 is driven by the worm shaft 20 torotate clockwise, the lead screw 40 drives the telescopic pipe 50 toretract towards the interior of the outer pipe 60. In FIG. 7, eachgripper arm 722 pushes the intermediate ring 75 and each rolling needle74 to rotate, such that the rotation direction of the torque spring 76is the same as the rotating direction of the worm wheel 31, and thepositioning section 761 is fixed into the notch 653 of the half cover651 (as shown in FIG. 5), and the torque spring 76 produces a bindingforce to latch and stop the intermediate ring 75 (In other words, theintermediate ring 75 is held securely without being rotated), such thateach gripper arm 722 drives each rolling needle 74 and increases thefriction of the intermediate ring to reduce the rotation speed of thelead screw 40. Therefore, when the linear actuator is installed to anelectric bed or chair, the speed for the telescopic pipe 50 to beretracted into the outer pipe 60 is slower in order to improve theuser's comfort.

When the worm wheel 31 is driven by the worm shaft 20 in an oppositedirection and rotated counterclockwise, the lead screw 40 drives thetelescopic pipe 50 to extend out from the outer pipe 60. In FIG. 7, eachgripper arm 722 pushes the intermediate ring 75 and each rolling needle74 to rotate. Since the rotation direction of the torque spring 76 isopposite to the rotation direction of the worm wheel 31, therefore thetorque spring 76 will be loosened by the rotation of the intermediatering 75 easily. Now, the friction damp among the intermediate ring 75,the torque spring 76 and each rolling needle 74 is small, so that theintermediate ring 75 can be rotated inside the torque spring 76 easily,and the internal mechanisms can have a good transmission effect.

In summation of the description above, the high-load linear actuator ofpresent invention improves over the prior art and complies with thepatent application requirements, and thus is duly filed for patentapplication.

While the invention has been described by means of specific embodiments,numerous modifications and variations could be made thereto by thoseskilled in the art without departing from the scope and spirit of theinvention set forth in the claims.

What is claimed is:
 1. A high-load linear actuator, comprising: adriving mechanism, having a base and a motor rotated clockwise andcounterclockwise, and the base having a supporting portion and anaccommodating portion, and the supporting portion having a seat and ahollow cylinder formed and extended from the seat, and the accommodatingportion having a ring body coupled to the hollow cylinder, and the motorbeing mounted onto the seat, wherein the accommodating portion furtherincludes a cover plate covering the ring body at an open side of thering body, a rear step is formed on a surface of the ring body at aninternal side opposite to the open side, and a front step is formed on aside of the cover plate and at a position corresponding to the rearstep; a worm shaft, protruding from the motor and passed into the hollowcylinder; a worm wheel assembly, having a worm wheel and two bearingsfor jointly supporting the worm wheel installed inside the ring body,wherein the worm wheel has a circular tooth flank engaged andtransmitted with the worm shaft, a hollow axle is coupled to thecircular tooth flank, a front containing groove and a rear containinggroove are formed in the circular tooth flank to surround the hollowaxle at two opposite sides of the circular tooth flank respectively, thecircular tooth flank has a plurality of external gear teeth to surroundthe front containing groove and the rear containing groove, the twobearings are embedded in the front and the rear containing grooves andsheathed on opposite ends of the hollow axle respectively, one of thetwo bearings is installed and contained in between the front containinggroove and the front step, and the other of the two bearings isinstalled and contained in between the rear containing groove and therear step; a lead screw, passed through and coupled to the worm wheel,and actuated by the motor to produce a rotation; a telescopic pipe,sheathed onto the exterior of the lead screw and screwed with the leadscrew; a retardation transmission mechanism, and the retardationtransmission mechanism comprising a driven gear, a gripper ring, adriven bushing, a plurality of rolling needles, an intermediate ring anda torque spring, and the driven gear being sheathed and coupled to thelead screw and passed and coupled to the worm wheel, and the gripperring is sheathed and coupled to the driven gear for linking the wormwheel and the driven gear synchronously, and the driven bushing beingsheathed and coupled to the lead screw and passed and coupled into thegripper ring, and the rolling needles being passed and coupled betweenthe driven bushing and the intermediate ring, and the torque springbeing provided for binding the external periphery of the intermediatering by an elastic force; and an outer pipe, sheathed onto the exteriorof the telescopic pipe, and the telescopic pipe being driven by the leadscrew to linearly extend or retract with respect to the outer pipe. 2.The high-load linear actuator of claim 1, wherein the ring body and thehollow cylinder are integrally formed.
 3. The high-load linear actuatorof claim 1, further comprising a rear supporting mechanism, and the rearsupporting mechanism comprising two half covers and a roller bearingclamped by the two half covers, and the roller bearing being providedfor passing, coupling and installing the lead screw.
 4. The high-loadlinear actuator of claim 3, wherein the retardation transmissionmechanism is sheathed and coupled to the lead screw and is disposedbetween the rear supporting mechanism and the worm wheel assembly. 5.The high-load linear actuator of claim 4, further comprising a housingcovered onto the exterior of the driving mechanism, the rear supportingmechanism and the retardation transmission mechanism for passing andcoupling a lateral side of the outer pipe.
 6. The high-load linearactuator of claim 5, further comprising an electric unit installed inthe housing and disposed at a lateral edge of the motor.
 7. Thehigh-load linear actuator of claim 1, wherein the hollow axle of theworm wheel includes a plurality of internal gear teeth, and the drivengear includes a plurality of external gear teeth latched with theinternal gear teeth respectively, and the gripper ring also includes aplurality of ratcheted grooves for latching the external gear teethrespectively.
 8. The high-load linear actuator of claim 1, wherein thegripper ring includes a plurality of gripper arms and a separating slotformed between any two adjacent gripper arms, and the driven bushingincludes a plurality of protruding stripes extended from the externalperiphery of the driven bushing and a ditch formed between any twoadjacent protruding stripes, and the rolling needles are contained in aspace enclosed by the separating slot and the ditch, and the rollingneedles are installed and enclosed by the intermediate ring.
 9. Thehigh-load linear actuator of claim 1, wherein the lead screw has anexternal positioning plane, and the driven bushing has an internalpositioning plane latched with the external positioning plane.